I mean there's also a famous counterpart in the sciences--biologists popping off on why we need to invade Iraq right now, minor astronomers screaming at Renaissance historians that they outrank them, science vigilantes threatening to get anyone investigating that big 65MA crater in Mexico fired for woo-woo: they have to be not just an expert, but a guru

it's basically a pretension to universality: someone's mastered some arcane psychoanalysis, now they think they should tell chemists how to do their job; someone knows physics, now she's an expert in US culture or the Syrian Civil War (yes, I can give names)